Anaesthetic apparatus

ABSTRACT

An anaesthetic apparatus for analgesic narcosis using a mixture of oxygen gas and nitrous oxide gas, said apparatus being equipped with an inlet valve for the oxygen gas, a pressure regulator for same, a pressure-controlled balance regulator for the nitrous oxide gas and a proportioning valve for regulation of the oxygen nitrous gas mixture, which apparatus is executed as a homogenous block and in which the connections between the components are arranged as internal channels.

United States Patent [1 1 Andersson 45] July 24, 1973 ANAESTHETIC APPARATUS [75] Inventor: Lennart Valentin Andersson,

Handen, Sweden [73] Assignee: Mediada AB, Gateborg, Sweden [22] Filed: Oct. 30, 1970 [21] Appl. No.: 85,633

[30] Foreign Application Priority Data Mar. 9, 1970 Sweden 3076/70 [52] U.S. Cl. 128/188 [51] Int. Cl A61m 16/00 [58] Field of Search 128/188, 142, 142.2,

[56] References Cited UNITED STATES PATENTS 3,068,879 12/1962 Snowman 137/81 3,474,812 10/1969 Robertson 137/98 X FOREIGN PATENTS OR APPLICATIONS 305,720 2/1969 Sweden 966,941 3/1950 France 128/188 Primary Examiner-William E. Kamm Assistant Examiner-G. F. Dunne Att0rney-Richard C. Sughrue, Robert .1. Seas, Jr.

et al.

[57] ABSTRACT An anaesthetic apparatus for analgesic narcosis using a mixture of oxygen gas and nitrous oxide gas, said apparatus being equipped with an inlet valve for the oxygen gas, a pressure regulator for same, a pressure controlled balance regulator for the nitrous oxide gas and a proportioning valve for regulation of the oxygen nitrous gas mixture, which apparatus is executed as a homogenous block and in which the connections between the components are arranged as internal channels.

3 Claims, 1 Drawing Figure PATIENT 1 ANAESTHETIC APPARATUS The invention applies to an anaesthetic apparatus for analgesic narcosis using a mixture of oxygen gas and nitrous oxide gas. Anaesthetic devices of this kind using a pressure regulator for the oxygen gas pressure, a membrane-influenced balance regulator, controlled by the oxygen gas pressure, for the nitrous oxide gas pressure, a proportioning valve for regulation of the nitrous oxide/oxygen gas mixture and an oxygen gas supply regulation valve are well-known.

Devices of this type are intended for connection either to a central gas supply, in which pressure is generally maintained at 4 i 2 at overpressure, or, via a pressure regulator, to gas cylinders with a much higher pressure. These devices are adjustable for gas mixtures containing 30-l00 percent oxygen gas by volume, the remainder being nitrous oxide gas. With a loss of ni trous oxide gas supply they only provide pure oxygen gas as long as the supply lasts.

In addition to connectors for oxygen and nitrous oxide gases there is generally a connection for a face mask and a connection for a reservoir bag.

Such anaesthetic devices are subject to stringent safety regulations. Thus, placing a check valve between the reservoir bag and the face mask to prevent rebreathing into the device is well-known. The provision of a fixed locking device to prevent any percentage setting less than 30 percent oxygen gas by volume so as to obviate the risk of suffocation is also well-known. With a 100 percent oxygen gas by volume setting, oxygen gas is generally supplied independently of the supply of nitrous oxide gas, thereby making oxygen gas therapy possible with anaesthetic devices of this kind. Quickrelease connectors are good fittings for connecting oxygen gas and nitrous oxide gas to the apparatus. Noninterchangeable connectors are used which may also be colour coded and have engraved or similarly marked information on gas type. Moreover, such anaesthetic devices contain provisions to prevent the flow of nitrous oxide gas to the oxygen gas connection and vice versa through the use of check valves and/or balance regulators which reduce the pressure of inflowing nitrous oxide gas to a levelnot exceeding the oxygen gas inflow pressure or preferably somewhat less than said pressure.

Even though known anaesthetic devices satisfy existing safety regulations, there is still room for further improvement and improved safety measures.

The object of the present invention is to improve and reduce the cost and size of known anaesthetic devices and to provide increased security.

According to the invention, therefore, a design for anaesthetic devices is proposed having no moving or loose parts which might involuntarily rub against each other or which people or objects could catch on, thereby inducing leakages. Furthermore, according to the invention it is proposed to separate the gases via a pressureless chamber or the like, connected to the atmosphere, in cases where the components are touched by both oxygen and nitrous oxide gases under raised pressure.

An anaesthetic apparatus according to the present invention is, therefore, characterized by execution in one homogenous block made from e.g. aluminium, perspex or some other material, by connections between components being made of internal channels in the material and by having components such as valves, regulators, membranes etc., mainly fitted into holes or recesses in the material.

According to a further characteristic feature of the invention, the balance regulator for nitrous oxide gas pressure displays a double membrane between a chamber for the nitrous oxide gas and a chamber for the oxygen gas, said membrane having an intermediate space connected to the atmosphere.

According to another characteristic feature of the invention, a throttle valve is fitted after the balance regulator, said valve being controlled by the oxygen gas pressure prevailing after said balance regulator and an oxygen gas supply regulation valve, said throttle valve controlling nitrous oxide gasflow from the balance regulator, an interspace connected to the atmosphere being further arranged between a chamber for the nitrous oxide gas and one for the oxygen gas.

An operative example of the invention will now be explained with references to the accompanying drawing which provides a schematic, vertical cross-section through an anaesthetic apparatus with a reservoir bag. The requisite, conventional sealing; units are not shown.

By the lid 47 fitted to the recess 41 in a homogenous block 20 made of e.g. aluminium, perspex or other material, there is the connection 21 (only sketchily rendered in the drawing) in a recess 25' for nitrous oxide gas with a filter 22 and check valve 23, here in the form of a spring-loaded ball. In addition, there is a connection 24 for oxygen gas fitted to another recess 25 in the block 20, the external shape of said connection differing from the connection 21 for nitrous oxide gas, here indicated with a fin-like ring of greater diameter than that of connection 24 in general. Another way to make the connections 21 and 24 is to supply one with a lefthand thread and the other with a right-hand thread. A channel 27 leads from the oxygen gas connection 24 to an oxygen gas pressure regulator A arranged in a hole 29 in the block 20.

This pressure regulator A can be adjusted with an adjustment screw 28 which, via a tensioned spring and load sensor 30, can raise a valve 31 from a valve seat 33 against the pressure of a spring 32. The load sensor 30 is connected to a membrane 34, which is located between an upper pressure space 35 and a lower open space 36, preferably in connection with atmospheric pressure, in which the aforementioned spring and one end of the adjustment screw 28 are located.

Via an inlet valve 3, 37 the upper pressure space 35 is connected to an oxygen gas channel 4. The inlet valve consists of a valve seat 37and a valve body, here in the form of a valve rod 3 with a valve element shown near the bottom of the drawing A spring 38, which via a pin 39 in valve rod 3 strives to raise said rod3 from its valve seat 37, compensates for the weight of valve rod 3.

One end of a double-arm lever 16, which is swingably mounted on a pivot 19, is actuated by the end of valve rod 3 away from valve seat 37; the other end of this lever 16 is connected to a centre rod 15 of the reservoir bag 2 which mechanically senses the reservoir bags degree of filling. This bag 2 is attached to a downward pointing pipe socket 40 on a lever tube 14 surrounding the lever 16.

An air valve F with valve body 18 whose weight causes it to rest on the air valves valve seat (not rendered in detail in the drawing) is affixed to lever tube 14. In addition, a patient valve with a valve body 17 seated only by virtue of its own weight, is connected to the lever tube 14, thereby preventing re-breathing into the anaesthetic apparatus.

From the oxygen gas channel 4 there is a connecting channel 7 leading to a hole 41 for a balance regulator B provided in said hole 41, thereby limiting a chamber 42 for the oxygen gas. This chamber 42 is formed by the walls of the hole 41 and, on one side, by a membrane 43 on the other side of which a spacer and a coaxial spacer ring 10 are affixed, followed by a further membrane 45. A space 46 is formed between the membranes 43 and 45 which, via openings in the ring 10' and a hole 44 in the block 20, is in contact with the atmosphere. This makes it impossible for oxygen gas to intrude into the nitrous oxide gas line or for nitrons oxide gas to intrude into the oxygen gas line, even with punctures of both membranes 43 and 45.

On the side of membrane 45 opposite the spacer a load sensor 49 is fitted into a chamber 48 for nitrous oxide gas. The aforementioned nitrous oxide gas connection 21, the valve of the balance regulator B with its valve body 1 and valve seat 50 and a spring which loads the valve body 1 in the direction of closure are fitted into lid 47 of this chamber 48. From chamber 48 there is also a nitrous oxide gas channel 51 leading to a throttle valve C for the nitrous oxide gas. This nitrous oxide gas channel 51 may consist ofa radial hole in the lid 47 and an arc-shaped recess in the block 20.

The throttle valve C is fitted into a hole 67 in the block 20 which is closed off with a plug 68. Valve rod 3 and the oxygen gas channel 4 pass through a hole 67. Two connecting channels 8 lead from oxygen gas channel 4 to an oxygen gas chamber 55, one wall of which is formed by a membrane 9 which has a space 59 on one side which is connected to the atmosphere via a hole 58. In this space 59 on the side of the membrane 9 turned away from the oxygen gas chamber 55 there is a load sensor 61 with a leak-proof introduction through the housing 57 of the throttle valve at 60. The load sensor 61 is devised to lift a valve body 52 against the pressure of a spring 53 off the throttle valve seat via the membrane 9 when there is a certain over-pressure in the throttle valves oxygen gas chamber 55 and, thus, even in the oxygen gas channel 4. The valve body 52 is fitted into hole 69 in the block 20 which hole is closed off with a plug 56.

A connecting channel 62 in the block 20 leads from the throttle valves seat 54 to the anaesthetic devices proportioning valve D which is fitted into a hole 71 in the block 20. This proportioning valve D displays, i.e., an oxygen gas chamber 63 connected to the channel 4, a nitrous oxide gas chamber 64 connected to connecting channel 62, and an intermediate mixing chamber 65. Between the mixing chamber 65 and the oxygen gas chamber 63 there is an oxygen gas throttling slot 5; further there is a corresponding nitrous oxide gas throttling slot 6 between mixing chamber 65 and nitrous oxide gas chamber 64. The displaceable valve body 11 of proportioning valve D is fitted between said slots 5 and 6.

Axial displacement of the valve body 11 is produced via a threaded valve spindle 66, connected to valve body 11, which spindle can be rotated in a threaded body 72 in a hole 71 via a setting knob 70 of the proportioning valve D.

A channel 12 in the block 20 and a further connecting channel 13 in an upper lid 73 in the block 20 lead from the mixing chamber to the aforementioned lever tube 14 fixed to the lid 73 and thence to reservoir bag 2 and, via the patient valve, to the patient.

The anaesthetic apparatus described above works as follows: oxygen gas and nitrous oxide gas from gas cylinders or a central supply are connected to the device s respective connections 21 and 24 and introduced at a pressure of ca 4 i 2 at overpressure. The order in which thetwo gases are connected is unimportant. If nitrous oxide gas is connected first, it can go no further than to the valve 1, 50 of the balance regulator B. When oxygen gas is then also connected and introduced, the following takes place:

Oxygen gas pressure is reduced in the pressure regulator A to the pressure set with adjustment screw 28, e.g. 2 at overpressure. If the reservoir bag is not filled at the time, the inlet valve 3, 37 is open and oxygen gas due to overpressure flows through channel 4 and is impeded in the throttling slot 5 of the proportion valve D, and an over-pressure, which in the present case is somewhat under 2 at overpressure, builds up in channel 4. This pressure influences the membrane 43 of the balance regulator B, its spacer 10, the membrane 45 and the load sensor 49 which lifts the balance regulator's valve body 1 from its seat 50, permitting nitrous oxide gas to flow through to the throttle valve C.

Via the channels 8 the throttle valve C is, in turn, influenced by oxygen gas pressure developing in channel 4, causing the membrane 9 of the throttle valve C via load sensor 61 to lift the valve body 52 from its seat 54, permitting nitrous oxide gas to flow via the channel 62 to nitrous oxide gas chamber 64. The inflowing nitrous oxide gas accordingly acquires a pressure which is somewhat lower than oxygen gas pressure in the channel 4 because of the spring by valve body 1 of the balance regulator B.

Axial displacement of valve body 11 of the proportioning valve D via the setting knob and valve spin dle 66 balances the flow-through areas of the slots 5 and 6 and, accordingly, the flow velocity of both gas components so that the desired percentage mixture or pure oxygen respectively is obtained. By virtue of a provision using a familiar technique but not shown in the drawing, oxygen gas content is not allowed to fall below a certain minimum value, primarily not below 30 percent by volume.

The gases so mixed or, where applicable, oxygen gas almost reduced to atmospheric pressure, flow from the mixing chamber 65 via channels 12 and 13 through the lever tube 14 to the reservoir bag 2. The bag is shortened when filled and lifts its centre rod 15 upwards so that the valve rod 3 of the inlet valve is pressed downwards via the swinging lever 16 against the pressure of spring 38, closing off the flow of oxygen gas. The pressure in the channels 4, 7 and 8 terminates and the flow of nitrous oxide gas is, thus, cut off. Throughout this procedure the system is kept elastically sealed by means of the valve body 17.

When the patient takes a breath, this valve body 17 is lifted and the relatively mild over-pressure (e.g. 1,2 cm column of water) in the reservoir bag and the latters volume decline. Thus, the bag is extended in length once again, inlet valve 3, 37 is opened and the entire procedure is repeated.

If the reservoir bag 2 is empty because there is no oxygen gas, sub-pressure develops in the system with patient inspiration, thereby lifting the valve washer 18 of an air valve F, thus providing the patient with plain air.

Nitrous oxide gas pressure does not influence oxygen gas flow. According to the invention, the anaesthetic apparatus may, thus, also be connected to oxygen gas alone and used in the oxygen gas treatment of patients.

No backflow of gas to any gas cylinder is possible because of the back-pressure valve between the gas cylinder and the anaesthetic apparatus. An overflow of oxygen gas from a central gas supplys oxygen gas connection to the nitrous oxide gas connection is prevented by the check valve 23 built into the anaesthetic apparatus. But even if this check valve 23 should fail, no oxygen gas could intrude into the nitrous oxide gas line and no nitrous oxide gas could intrude into the oxygen gas line via the proportioning valve, as this valve s mixing chamber 65 is practically connected to the atmosphere via channels 12 and 13, lever tube 14 and reservoir bag 2. However, both nitrous oxide gas and oxygen gas have a palpable over-pressure at the inlet valve 3, 37 and the balance valve 1, 50 respectively. Neither gas component could force the other out of the way; gas pressure would be reduced to about atmospheric pressure if there were a hypothetical flow from the oxygen gas throttling slot 5 through mixing chamber 65 to the nitrous oxide gas throttling slot 6 or vice versa. In other words, pressure inthe connected oxygen and nitrous oxide gas lines is assumed to be greater than in the mixing chamber 65, which is equivalent to a provision offering protection against overflow.

Since the throttle valve C only opens the nitrous oxide gas supply if a certain minimum oxygen gas pressure exists or is exceeded, further security is provided. Possible leakage in the throttle valves membrane 9 cannot lead to gas overflow to another gas system because of the connection 58 with the atmosphere. Nor can leakage in the balance regulator B lead to gas overflow from one system to the other because of intermediate space 46 which is connected to the atmosphere via the hole 44.

The invention also produces a very compact, lightweight version of an anaesthetic apparatus, eg 5 X 5 X 15 cm (ca 2 inches X 2 inches X 6 inches), (not including the reservoir bag and lever tube), with simple attachment either to a wall or a stand.

In conclusion, the anaesthetic apparatus, according to the invention, has no loose or moving parts which could involuntarily rub against one another or be torn loose by people or objects (e.g. an instrument trolley) passing, thereby obviating the development of leakages or other drawbacks.

Thus, the invention provides greater security, particularly against leakages, and reduced space requirements with lower production costs.

What I claim is:

l. Anaesthetic apparatus for analgesic narcosis using an oxygen-nitrous oxide gas mixture comprising a pressure regulator for the oxygen gas, a. pressure-controlled balance regulator for the nitrous oxide gas said balance regulator includes a pair of spaced-apart membranes positioned between a chamber for nitrous oxide gas and second chamber for oxygen gas, said pair of membranes being separated by an intermidiate space connected to the atmosphere, a proportioning valve for regulation of the oxygen-nitrous oxide gas mixture, and an inlet valve for the oxygen gas, and a one-piece homogenous block having a plurality of holes and recesses formed therein from the exterior surface of said block,each of said valves and regulators being mounted in one of said holes and recesses formed in the block, said block further including a plurality of internal connecting passages and channels formed therein, said in ternal passages and channels adapted for operatively interconnecting the components mounted in said recesses formed in the block.

2. Apparatus according to claim. 1, characterized by a throttle valve controlled by the oxygen gas pressure prevailing after the inlet valve, said throttle valve being arranged after the balance regulator in the direction of the nitrous oxide gas flow and adapted to cut off or admit the nitrous oxide gas flow from the balance regulator, an intermediate space connected to the atmosphere being arranged between a chamber containing the nitrous oxide gas and an oxygen gas chamber.

3. Apparatus according to claim 2, wherein the proportioning valve is provided with an over-pressure chamber for the oxygen gas, an over-pressure chamber for the nitrous oxide gas, and an intermediate chamber which is connectable to both of said over-pressure chambers by adjustable throttle slots and is in further connection with the atmosphere through a reservoir bag means and with a connection for a face mask. 

1. Anaesthetic apparatus for analgesic narcosis using an oxygennitrous oxide gas mixture comprising a pressure regulator for the oxygen gas, a pressure-controlled balance regulator for the nitrous oxide gas ''''said balance regulator includes a pair of spaced-apart membranes positioned between a chamber for nitrous oxide gas and second chamber for oxygen gas, said pair of membranes being separated by an intermidiate space connected to the atmosphere,'''' a proportioning valve for regulation of the oxygen-nitrous oxide gas mixture, and an inlet valve for the oxygen gas, and a one-piece homogenous block having a plurality of holes and recesses formed therein from the exterior surface of said block,each of said valves and regulators being mounted in one of said holes and recesses formed in the block, said block further including a plurality of internal connecting passages and channels formed therein, said internal passages and channels adapted for operatively interconnecting the components mounted in said recesses formed in the block.
 2. Apparatus according to claim 1, characterized by a throttle valve controlled by the oxygen gas pressure prevailing after the inlet valve, said throttle valve being arranged after the balance regulator in the direction of the nitrous oxide gas flow and adapted to cut off or admit the nitrous oxide gas flow from the balance regulator, an intermediate space connected to the atmosphere being arranged between a chamber containing the nitrous oxide gas and an oxygen gas chamber.
 3. Apparatus according to claim 2, wherein the proportioning valve is provided with an over-pressure chamber for the oxygen gas, an over-pressure chamber for the nitrous oxide gas, and an intermediate chamber which is connectable to both of said over-pressure chambers by adjustable throttle slots and is in further connection with the atmosphere through a reservoir bag means and with a connection for a face mask. 